1. Field of the Invention
The invention relates to a single wafer type substrate cleaning method and a single wafer type substrate cleaning apparatus, more particularly to a single wafer type wet cleaning technique or system for applying a cleaning treatment to substrates such as semiconductor wafers one by one during the fabrication process as well as certain devices such as electronic parts and the like.
2. Prior Art
A so-called batch type wet cleaning system has been the principal method of cleaning substrates such as semiconductor wafers (hereinafter referred to simply as “Wafers”), whereby wafers stored in a carrier cassette are immersed in sequence in wet bench type cleaning baths arranged in series, or wafers are directly immersed in the cleaning baths through a transfer unit without being stored in a carrier cassette. However, semiconductor devices have reached the sub micron age, in that they are now micro-fabricated and highly integrated, such that the face of wafers has recently required a very high degree of cleaning density, and wafers which are not stored in a cassette have to be wet-cleaned individually in a sealed cleaning housing. To this end, a so-called single wafer type wet cleaning system intended to meet the requirement of a higher cleaning density has been developed.
Under the single wafer type wet cleaning system, wafers can be cleaned with the use of a simple and compact cleaning system in a relatively clean atmosphere where particles and the like do not settle or remain on the face of the wafer. This system is therefore practical to use for small scale production.
Under the single wafer type cleaning system, wafers can be cleaned by the application of various chemical fluids on the face of wafers in a predetermined order, and finally dried by a spin drying treatment whereby the wafers are rotated at high speed. However, there are cases where oxygen remains in the sealed cleaning housing during the drying treatment phase depending on the kind of chemical fluid used, such that the face of a wafer is prone to oxidization. Accordingly, improvement of the system is desirable.